Science Knowings: HTML Course For Social Media

HTML5 Web Workers

From HTML Events to Web Workers

We've explored HTML events and copywriting. Now, let's dive into HTML5 Web Workers, a technology that allows us to perform background tasks in parallel, enhancing website performance and user experience.

What are Web Workers?

Web Workers are JavaScript threads that run in the background, separate from the main user interface (UI) thread. They allow us to offload computationally intensive tasks, such as image processing or calculations, without blocking the UI.

Benefits of Web Workers

Web Workers offer several benefits:
• Improved website responsiveness: Offloading tasks to workers prevents the UI thread from being blocked.
• Enhanced performance: Parallelizing tasks speeds up operations that would otherwise slow down the UI.
• Increased scalability: Workers can be easily added to handle additional load during heavy processing.

Creating a Web Worker

To create a Web Worker, use the Worker() constructor and pass the URL of the worker script. For example:
var worker = new Worker('worker.js');

Communication Between Main Thread and Web Worker

Communication between the main thread and a Web Worker involves two methods:
postMessage(): Sends a message from the main thread to the worker.
addEventListener(): Listens for messages from the worker on the main thread.

postMessage() Method

The postMessage() method takes a message as an argument and sends it to the worker. For example:
worker.postMessage({ message: 'Hello from the main thread!' });

addEventListener() Method

The addEventListener() method listens for messages from the worker on the main thread. For example:
worker.addEventListener('message', function(e) { console.log(; });

Use Cases for Web Workers

Web Workers are particularly useful for:
• Optimizing images: Resize, compress, and apply filters without affecting the UI responsiveness.
• Performing complex calculations: Handle numerical or data-intensive computations in the background.
• Handling long-running tasks: Offload tasks that take a significant amount of time, such as fetching large data sets.

Optimizing Images

const worker = new Worker('image-worker.js');
imageWorker.postMessage({ image: myImage, width: 300, height: 300 });

Performing Complex Calculations

const worker = new Worker('calc-worker.js');
calcWorker.postMessage({ numbers: [1, 2, 3, 4, 5] });

Handling Long-Running Tasks

const worker = new Worker('long-task-worker.js');
longTaskWorker.postMessage({ url: 'data.json' });

Next Topic: HTML5 Application Cache

Next, we'll explore HTML5 Application Cache, a mechanism for caching web applications for offline use. Follow us to learn how to improve your website's user experience, even without an internet connection!